Using the Supplied Templates

Casting:

Materials including a cast sock or casting pants for an AK, indelible marker, plaster bandage, potentially a cutting strip and cast saw or blade and a cast spreader.  Flexible tubing is sometimes necessary above the patella on a BK.  The Syme’s cast would need to be spread open for removal; I usually cut and part it with a cast spreader along a cutting strip posteriorly.

Positioning:

• For Syme’s patients a 90-degree knee flexion is recommended allowing the heel pad to rest on a flat surface.  Don’t wrap above the mid patella circumferentially without using a figure of 8 type of wrap that leaves the back (and front) low for cast removal.  Flexible plaster bandage works best with this technique.  Minimum landmarks include the Mid-Patellar Tendon and the tibial crest.

• For BK patients a 45-degree flexion helps define the hamstring relief and bar more accurately.  Plaster splints above the mid patella leaving the back open will give you the medial and lateral height you want, while allowing for cast removal.  Minimum landmarks include the Mid-Patellar Tendon and the tibial crest.

• Position AK patients so they are lying on their side extended so they aren’t arching their back.  Aggressive casting works well to capture the femoral shaft and minimize lateral gapping.  A plaster splint works well for additional height proximally.  Mark the ischium, trochanter and femoral shaft.

Digitizing:

Trim away excess stockinet and use plaster bandage and prepare to close off the open part of the cast.  The proximal anterior portion on a BK will most likely cause a mechanical digitizer to bridge the patella if it was cast in a semi-flexed position.  A section should be cut and pulled out to allow clearance prior to closing off the open part with plaster.  If you rest the cast on a flat surface before the plaster sets to close the openings, it often helps to better orient the cast in the digitizer, especially on an AK.  The indelible marks in your cast should be darkened with a felt tip marker if you are using a mechanical digitizer.  Those marks will then be reflected on the model for reference.

Place the cast in the digitizer, bench aligned with the wheel resting anteriorly.  Use the MPT on a BK and pull the arm back bisecting the cast to make sure it isn’t skewed medially or laterally.  The posterior trim and bulge are linked to the MPT and will be placed directly behind even if the cast isn’t centered.

Landmarks and Adjustments:

Before applying a template, apply the appropriate landmarks and smooth out any rough areas using the region tool or global blend.  Apply the desired template and modify as necessary.  Confirm that the fibular head relief is located correctly as it is linked to the MPT, not a fibular head landmark unless your own template requires one and it is linked accordingly.  It is very important to check the length of the socket designed, comparing it to the actual residual limb length measured and make any required adjustments to the model.  A trans-tibial socket will usually need an additional 5-10mm added by stretching between the top and the bottom of the tibia.  A trans-femoral socket as measured from the ischium often needs about 20mm of additional length.  A Syme’s shouldn’t need much length adjustment, just confirm that the distal end is reflected accurately and wasn’t capped inappropriately.